Kim Brooks dons the tackiest holiday sweater she can find. She tops the outfit with a Santa hat and starts snapping her camera furiously. She coos, clicks her tongue and sings “I’ve Been Working on the Railroad.” She’ll do anything to get kids to give her that killer smile while sitting on Santa’s lap.

So goes a day in the life of Santa’s shutterbug, a gig that involves coping with crying kids, anxious parents and an overheated guy in a red suit.

“We are so busy this time of year,” says Brooks, who runs Big Apple Portraits on the Upper West Side, an outfit that specializes in shoots with Kris Kringle.

Starting in early November, photographers of Santa face packed weekends with back-to-back shoots of kids and St. Nick. The frenzy doesn’t stop until Christmas Day, when the holiday cards have been mailed and Santa has returned to the North Pole.

The seasonal job has more to do with being quick and comfortable with children than being the best photographer, because — let’s face it — Santa is one scary dude for small kids.

“I try not to hire professional photographers,” says Danny Neron, who hires and trains photographers for Noerr Programs. The events company places Santas in stores across the country and has seen demand for Santa sessions on the rise, expanding to 40 more locations this year.

“Photographers have a sense of portrait and poses, not about capturing the moment. A studio photographer may spend 30 minutes on a shoot — we have one.”

Neron, who’s based in Connecticut, is no novice: He’s spent the last 16 years as a seasonal photographer, doing stints at Roosevelt Field Shopping Mall in Garden City, LI, The Plaza in Midtown and SkyView Center in Flushing.

“I’ve never had a child pee or puke on Santa, but it happens,” adds Neron.

He’s witnessed surprise marriage proposals on Santa’s lap and has had the occasional brush-in with celebrity clients — three years ago, LL Cool J came for a Santa shoot in Roosevelt Field, and Tom Cruise showed up at The Plaza two years ago, says Neron.

He has had kids dart off Santa’s lap and run behind the camera — “Luckily, the sets don’t let them get too far!” he says.

Still, the photographer’s job is physically demanding. Shooters are on their feet for up to eight hours, with only brief breaks for water and food. In between snapping photos, they are picking up babies, distracting them with squeaky toys and hopping around to get the best angle.

“You are jumping around, screaming, ‘Smile!’ constantly. You need a break,” says Neron, who recharges by drinking lots of water to revive his voice and props up his feet at the end of the day.

The pay is peanuts compared to portrait photography, according to George Delgado, a teacher at the New York Institute of Photography. Still, he does a few Santa jobs a year for the pure enjoyment of it all.

“It’s the one time of year they can get together and get a professional photo at a low price,” he says. In his 10 years of Santa stints, his biggest disaster was last year, when a drug store in Harlem decided to use a Santa wearing an Obama mask. “It freaked out the kids,” he recalls. “There was a lot of screaming and refusal to get near Obama Claus.”

But skilled shutterbugs have a few tricks up their sleeves to calm crazed kids. Neron blows air in their direction to distract them briefly. Once they stop crying, he takes a quick shot. Delgado chats up the kids, asking who their favorite cartoon characters are so they loosen up. Brooks, on the other hand, sings songs.

After all, the goal is to make the experience painless for children while capturing their priceless reactions to Santa for parents, who will cherish the moment for decades to come.

“You form a bond with families. They come back to the same place because they want the same Santa,” says Neron. “It’s a tradition, and you are part of that tradition.”